doe co2 injecting hurt your fish?

[Roan Art]

Every rapid change makes a shock. Do it gradualy and there is no shock. Start from your selfs, go into a room thats -20 C on a summer day and you will shock, but in the winter its a normal temperature. Ofcourse this doesn't have anything with ph its just a analogy.

And doesn't have anything to do with pH, as you said

Roan

 

[RTR]

You can drop pH up to a full log (pH 7.0 to 6.0, or 8.0 to 7.0) by CO2 addition, and allow it to revert to baseline during the dark cycle and the fish will never notice or care. But if you do comparable changes to the TDS you will have osmotic shock if done rapidly (as by bicarb addition or phosphate buffer affition to do the same pH change). The so-called pH shock is a misnomer, there is no such thing without psmotic changes. Osmotic shock is real and can be a big issue for captive fish.